i am also a bartender and would never think about doing that! if a person writes down a tip and adds wrong, i go in favor for the customer. if they write down a $5.00 tip but only add it up to $4, i only take the $4. kwim? i had a horrible server one time and i got a discount at this restaurant. so, in order to receive the discount, we have to automatically tip 20%. well, the service was HORRIBLE! i decided not to use my discount and let her $0. for a tip. she wrote in her own tip on the cc receipt. as soon as i noticed this, i went to the restaurant with my receipt and talked to the manager. he brought the waitress into the meeting and promptly fired her. i always write a 0 with a line through it for a tip and leave cash. she wrote in a 10.00 tip. i got my money back, she got fired, and the manager offered me a job. it is very wise to check your statements, there are alot of dishonest people out there. you all can come sit in my bar anytime and never have to worry about this happening to you!